Oxidation catalysts comprising metal-complexes are well known. One class being macrocyclic ligands, which co-ordinate with a transition metal ion. Such catalysts have been used in laundry compositions as parts of a bleaching system. These catalysts activate H2O2 or other peroxygen sources in water, and are effective at neutral to basic pH.
A catalyst is disclosed in WO 98/03263, filed Jul. 21, 1997, (Collins), which comprises a macrocyclic (tetra) amido N-donor. The macrocycle is capable of complexing with a metal ion, for example an iron III or IV. The complex also comprises axial ligands, for example as chloride or water, and one or more counter ions, for example tetraphenylphosphonium and tetraethylammonium.
U.S. Pat. No. 5,853,428, filed Feb. 24, 1997, (Collins) discloses use of similar catalysts in laundry detergent compositions.
Bleaching catalysts are of particular utility in the prevention of so-called ‘dye transfer’. This occurs when dyestuffs are released from one region of a cloth article during laundering and later re-adsorbed at another location or on another article. It is advantageous to bleach the dyestuff while it is in aqueous solution, thereby preventing or reducing its transfer.
For reasons of toxicological and environmental acceptance, it is preferable that the axial ligands and counter-ions are relatively benign. Ions such as trifluoroacetate, tetra-phenylphosphonium and tetra-ethylammonium are not preferred where they would typically come into skin-contact as a consequence of use.
Several synthetic routes are known for the preparation of the catalysts described in the ‘Collins’ patents. In one such route, described in U.S. Pat. No. 6,051,704, Filed Jul. 22, 1996, an alpha or beta amino carboxylic acid, for example a alpha-amino isobutyric acid, is reacted with an activated malonate or oxalate derivative, for example a di-methyl malonyl chloride, with mild heating. Upon completion of a double coupling reaction, hydrolysis of the product yields a diamine-containing intermediate, a macro linker. In a further step, a diamine, typically an ortho-phenylene diamine, is reacted with the macro linker in the presence of a coupling agent to form a tetra-amido macrocycle. The macrocycle is subsequently complexed with a metal in the presence of appropriate ligands.
The synthetic route described in the ‘Collins’ patents is believed to produce a relatively low yield of a relatively impure material, and is believed unsuitable for large scale use.
An azide based synthetic route to macrocyclic tetra-amido ligands is described in Uffelman, E. S., PhD Thesis (California Institute of Technology, [1992]). This is described in further detail in U.S. Pat. No. 5,853,428, filed Feb. 24, 1997.
A further synthetic route is disclosed in U.S. Pat. No. 6,127,536 (Deline et al., filed May 25, 1999, issued Oct. 3, 2000). In this synthesis 1,2-phenylenediamine is reacted with 2-bromoisobutyryl bromide to form a precipitating intermediate which is cyclised by reaction with diethyl malonyl dichloride.